RGB Royal Blue (R0 M0 B255) no equivalent in CMYK: what about commercial printers?

RGB Royal Blue (R0 M0 B255) no equivalent in CMYK: what about commercial printers?

Post by glutinou » Mon, 18 Oct 2004 18:08:11


I've got this logo which is pure blue in RGB mode i.e. R0 G0 B255
(hexadecimal 0000ff), and my client wants to use it for stationery.

Corel simply won't allow it unless I uncheck 'simulate printer
colors', and any conversion to CMYK results in a much darker blue.

I can't believe it's not possible to print this hue, but I'm at a loss
to understand what the problem is. It's just a bright blue, isn't it?
I mean, if someone was wearing that shade of blue in a photograph,
wouldn't that be accurately printable?

Any ideas, hints, URLs or detailed explanations most welcome!

Thanks
 
 
 

RGB Royal Blue (R0 M0 B255) no equivalent in CMYK: what about commercial printers?

Post by Hunter Ell » Mon, 18 Oct 2004 22:14:52


RGB colors have a larger gamut than what can actually be printed. You need
to start learning the differences between CMYK and RGB, between onscreen
images and images for printing. This article should help a bit:
http://www.yqcomputer.com/

 
 
 

RGB Royal Blue (R0 M0 B255) no equivalent in CMYK: what about commercial printers?

Post by glutinou » Tue, 19 Oct 2004 18:48:40

On Sun, 17 Oct 2004 13:14:52 GMT, "Hunter Elliott"





Hello Hunter,
Not the first time you've stepped in on something I've been struggling
with! Thank you...

I'm acquainted with the basic ideas of CMYK/RGB incompatibility.
What puzzles me is that I can't really find a decent bright blue in
the CMYK gamut, but if I convert an RGB scanned photograph with lots
of blue in it to CMYK, I don't expect some of the blues to
dramatically diverge from the original, and - say - become much much
darker. I expect the photograph to remain pretty much the same, and
that therefore it should be possibe to print a decent bright blue

So I'm guessing there is a way to approach most shades of anything,
but as ever, I'm prepared to discover that I'm 100% wrong!
 
 
 

RGB Royal Blue (R0 M0 B255) no equivalent in CMYK: what about commercial printers?

Post by Hunter Ell » Tue, 19 Oct 2004 20:17:42


Well, not to be rude, but you've definitely contradicted yourself here. If
you're familiar with the differnces between RGB and CMYK, between an
additive colorspace and a subtractive colorspace, between a projected
colorspace and a reflective colorspace, how can you go on to say that you
expect an RGB scan of a photo which is then converted to CMYK to print the
same as the original? It's gone through a process that can't really print
all of the colors because they're outside the range of the colormodel.

You might want to read up on the tips here: www.scantips.com and
www.retouchpro.com may have some info for you, too.


Some may depend on the color profile you may or may not be working with. Are
you sending this out to be printed or are you trying to use a home-use ink
jet printer? If inkjet do you have 4 separate cartridges for colors or just
2? Have you considered getting the new 6 and 7 color printers? Some actually
have a "blue" and "red" cartridge to help with RGB images (allegedly). Are
you using photo paper or plain paper? Glossy or matte? Also, what dpi/ppi
level are you scanning at? I'm not saying I have the answers for these
things... But they're items to look at.

Now if you're converting things to a single color, you could always look at
Pantone color systems.
 
 
 

RGB Royal Blue (R0 M0 B255) no equivalent in CMYK: what about commercial printers?

Post by Craig McWa » Wed, 20 Oct 2004 01:19:28

The color you see in R0 G0 B255 simply doesn't exist in CMYK-not even close.
A direct conversion (force fit) to CMYK gives you 100C 100M which prints a
dark purple. Something around 100C 70M comes pretty close. The best thing to
do is to get a CMYK swatchbook and pick a color that *looks like* what you
are seeing onscreen. Maybe go to a Pantone if you really need a strong blue.

Craig
 
 
 

RGB Royal Blue (R0 M0 B255) no equivalent in CMYK: what about commercial printers?

Post by glutinou » Tue, 26 Oct 2004 00:01:02

On Mon, 18 Oct 2004 11:17:42 GMT, "Hunter Elliott"





Hello again...

No, by any ordinary standard you're far from being rude, and by usenet
standards you're a charmer...

I didn't say I expected a photo to print out the same: only that
whenever I convert a photographic image from RGB to CMYK, I've never
seen a colour diverge so seriously from the original the way that RGB
'pure' blue does (as an example).


Okeydokey, thanks.

I have a colour profile chart from the commercial printer this
particular job is going to, and c100 m25 seems as near as we can get.

My original mistake was to produce some prototype logos and slap on a
few colours, including this damn blue, not in the least expecting my
client to seize upon such a gaudy shade with such enthusiasm. That's
my main lesson from this episode. Why RGB? The main demand was for
the website to be up and running.
 
 
 

RGB Royal Blue (R0 M0 B255) no equivalent in CMYK: what about commercial printers?

Post by glutinou » Tue, 26 Oct 2004 00:03:41

You're not kidding. Like I just wrote to Hunter, this troublesome
blue wasn't really intended as a serious proposal to my client: I was
just playing around with some prototype logos and really disn't think
anyone would choose such a vivid colour. Nearest I've come is c100
m25 or thereabouts. And one unhappy client who thinks I'm being
awkward.... :-/